The present invention relates to a sorter for sorting and collating copy sheets which are sequentially discharged from a copier, a printer and other image-forming apparatus. More particularly, the present invention is concerned with a sorter which sorts and collates copy sheets by use of a mechanism for driving bins sequentially toward a copy outlet of an imageforming apparatus to load them with copy sheets.
A bin driving mechanism of the king described is generally implemented with Geneva wheels each being provided with a notch, or with so-called helical cams each being provided with a helical recess therearound, and others. Such a movable bin type sorter is simpler in construction and smaller in weight than a fixed bin type sorter which includes a group of bins arranged stepwise and fixed to the body of the sorter, and deflecting means for distributing incoming copies to predetermined bins. With such advantages, a movable bin type sorter is generally suitable for use with small and medium size copiers.
For example, a prior art movable bin type sorter with a stepwise bin driving mechanism includes a group of bins each having cam members at both sides of its outermost end, and pins protruding sideways from both sides of its innermost end. The bin driving mechanism is implemented with a pair of helical cams each being provided with a helical cam therearound for engagement with the pins of the bins, the helical cams being driven by a bin drive motor. A bin unit is provided with guides in which the pins are received, the lowermost bin in the bin group being fixed to the bin unit. A bin unit biasing mechanism which is implemented with a resilient member is loaded between an upper portion of the sorter and the innermost end of the lowermost bin so as to constantly bias the bin unit upward. A bin feeding mechanism adapted to surely feed the bins step by step is provided with a pawl for catching each of the pins. Further, a sheet transporting mechanism is provided for transporting a copy sheet as the copy sheet is discharged from a copier or like image-forming apparatus to which the sorter is connected.
The prior art sorter constructed as described above has various disadvantages as enumerated below.
(1) The bin unit biasing mechanism and bin feeding mechanism which are essential add to the intricacy of construction and cost.
(2) The removal of the bins from the sorter body is not easy and, therefore, the efficiency of repair and maintenance is poor. In addition, since the bins are transported for delivery and others packed together with the sorter, they are apt to be damaged or deformed during transport and the packing work is time- and labor-consuming.
(3) To promote light-weight construction of a sorter, all of the bins except for the lowermost one are made of aluminum alloy or like material. The lowermost bin serves not only as a bin for loading copy sheets but also as the bottom plate of the bin unit and a support member for supporting the other bins. For this reason, the lowermost bin is made of a material whose sectional coefficient is greater than that of the other bins. The bins other than the lowermost one are flexed by the weight of copy sheets stacked therein until the spacing between the nearby bins, i.e., the space available above each bin decreases beyond a predetermined one. Although such seemingly lowers the stacking ability, those bins which are made of the same material undergo the same amount of flexure and, therefore, accommodate a predetermine number of copy sheets each. On the other hand, the lowermost bin having a relatively large sectional coefficient undergoes little flexure compared to the others and, therefore, cannot be provided with a space thereabove which is great enough to accommodate a predetermined number of copy sheets. In the light of this, there has been proposed an arrangement in which a support frame is provided below the lowermost bin while all the bins inclusive of the lowermost bin are made of the same material, and an arrangement in which the cam members at the outermost end of the lowermost bin are bent to a greater height than the others to define beforehand a greater space above the lowermost bin than above the others (Japanese Patent Laid-Open Publication (Kokai) No. 59-227659). However, even such alternative schemes invite increases in size, weight and cost.
Another sorter of the type described known in the art includes means for sequentially moving a bin group step by step, and means for opening each bin to accommodate an incoming copy sheet therein and constructed independently of the opening means, as disclosed in Japanese Patent Laid-Open Publication Nos. 59-158762 and 59-158764.
Meanwhile, in a movable bin type sorter with a stepwise bin driving mechanism of the type stated, the bin driving mechanism driven by a drive motor moves a predetermined one of multiple bins to an inlet position where a copy sheet is discharged from an image-forming apparatus. To hold the particular bin at the discharge position, it is necessary for the drive motor to be braked for a moment. Means for braking the drive motor so has heretofore been implemented with a brake shoe attached to the rotor of the drive motor, or an electromagnetic brake combined with the drive motor. A problem with the brake shoe type scheme is that a predetermined brake torque is unachievable unless the motor current is increased and, in addition, the braking force is unstable. The electromagnetic brake type scheme, on the other hand, is disadvantageous in that the braking force becomes unstable in the buildup stage of the clutch, the freedom of design is limited due to the limitations on the arrangement of various parts, and the apparatus becomes bulky.
A copy sheet discharged from a copier or like imaging apparatus may be stiffened in order to ensure positive discharge, as often practiced in the art. Specifically, one-roller of each transport roller pair is provided with flanges at both sides thereof to provide a copy sheet with shallow folds each extending in an intended direction of sheet transport. In some sheet discharge mechanisms, however, a sheet discharge path is formed such that the direction of transport defined by a sheet guide member is deflected at a point just before a point of discharge, owing to the arrangement of various parts and the direction of sheet discharge which are particular to the mechanisms. In such a case, should a copy sheet be stiffened by the customary method, the paper would fail to accurately follow the deflection of the path and bend at its stiffened portions to be thereby creased or otherwise disfigured and/or produce annoying noise. For this reason, a sheet discharging mechanism having a deflected section as stated has not been furnished with stiffening means. It, therefore, has often occurred that thin sheets, sheets which are easy to gather static electricity, and the like cannot be discharged positively due to the instability of transport direction.